Cathode ray telautograph



Dec; 31, 1940. HANDRICK CATHODE RAY TELAUTOGRAPH Filed June 21, 1939 io J NR R

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N Mn H I H mm E Patented Dec. 31, 1940 2,227,083 CATHODE my TELAUTOGRAPH M Erich Handrick, Berlin, Germany, assignoito General Electric Company, a corporationoi' New York Application June 21, 1939,.Serial No. 280,320 j I In Germany July 19, 1938 i r The invention relates to a noye'l apparatus for transmitting letters, drawings, sketches and the like with the aid of a cathode ray tube.

The object of the invention ,isto provide an 5 arrangement. having a cathode ray tube with two deflection systems for deviating the produced electron ray in two different directions extending preferably at right angles torone anothen A resistance layer is provided as is. also an electrically conductive point or stylus by means of which the image isdrawn upon the resistance layer before being transmitted. The deflection systems of the cathode ray tube are conductingly connected with thesaid resistance layer and are arrangedin a bridge circuit fed from a direct current source so that movements of the point over the resistance layer may cause corresponding movements of the electron ray over the fluorescent screen of the tube. l

20 The invention maybest be explained by referring to the drawing wherein like reference characters represent like parts and wherein:

Figure 1 shows schematically a preferred form of the present invention; 1

Figure 2 shows a detail modification of a portion of Figure 1'; 1

Figure 3 shows one system for suppressing the cathode ray beam under certain circumstances, and

Figure 4 shows a modification of the system shown in Figure a 7 i In Figure 1, item I represents schematically a tube having four deflection plates. Each pair of deflection plates is bridged by resistors, namely one of the plate pairs by the'resistors l and H and the other pair of plates by the resistors i2 and I3. The centers of the resistors bridging the pairs ofdeflection plates have connections to the negative pole of a direct current source 2 while the other pole has the point or stylus B consisting of conductive material, connected thereto across a relay winding 9. This point serves for drawing. a picture on the'resistance layer 3 of l which a part 4 is a smooth plate suited for writing or drawing the picture to be transmitted with the arrangement. To this end, four contacts i arearranged upon the resistance plate 3 in a uniform distribution in the vicinity of the border of 3 of which each is connected to a respective plate of the deflection systems of the tube l. A pair of deflection plates is connected with opposite contact electrodes 7.

Now, if the writing member or stylus 6 comes in contact with a point of the resistance layer 3 the direct current source '2 passes a current 2 Claims. (oi. 178-18) through the deflection plate resistances, the writ- .ing member 6 and the resistance layer-3 placed in a bpidge circuit. The current in the diilerent branches of the bridge then depends on the resistance existing between the contact point of 5 ;the writing member and ,.-the individual contacts I; in other words it depends upon the position of the writing member on the layer 3. Hence, potentialsappear at the-resistors l0, H, l2 .-l3 which are applied-to the pairs of deflection plates 10 thus efiectinga displacement or deflection of the electron ray beam of thetube on the screen to a pointwhich corresponds to the position of the writing member on the resistance layer. If for instance the writing point is situatedin the cen- 5 ter of 4,.the potentials appearing at opposite ends of the resistors l0 and II are equal in intensity and accordingly the beam is not deflected. The sameis true as regards the potentials at resistances l2 and 13. Therefore; the electron rayim- 2o pinges the center of the fluorescent screen without having been deflected. If, however, the writing point is in the vicinity of one of the electrodes 1, the potentials at theresistors I 0, ll, 12 and I3 are such that they effect a maximum adjustable displacement of the electron ray determined by the magnitude of the direct current source. Hence, as the writing member moves over the layer dythe electron ray carries out corresponding movements on the fluorescent screen, i. e., 80 the pictures drawn by the writing member are rendered visible on the. fluorescent screen and transmitted thereto. The images appearing on the fluorescent screen therefore are sufiiciently true to scale, but it should be borne in mind in this cOnnGctionthat the fidelity of the transmission isthe higher, the smaller the surface 4 and the greater the symmetryof the latter with respect-to all contacts 1. But if it is desired to have the surface! aslarge as possible, it is advisableto provide a resistance layer which. varies "all over in its thickness from point to point instead of. having the same thickness so thatdistortions oi the picture due to the transmission will be compensated.

Figure 2 shows an example of a modification of the arrangement according to the invention. An elastic metal foil is spanned between the mounts l5 and I6 above the resistance layer 3 and the table 4. This foil carries a piece of writing paper H. The tensioned foil takes the place of the writing member Bin that for instance the mounts l5 and I6 are connected to the direct current source 2. Now when writing on the paper H by any desired instrument the toll is pressed against the resistance layer 3 so that a current can pass through the bridge circuit and which produces potentials at the deflection plates in the manner described. 2

The relay 8 serves for controlling the beam intensity, and accordingly the brilliance of the tube, at writing, in fact it the writing organ touches the resistance layer, the relay is actuated and short circuits a negative biasing potential placed at the beam intensity control electrode of the tube, said potential preventing the appearance of the luminous spot on the screen when the apparatus is out 01' operation.

The control of the cathode ray beam may best be explained by referring to Figure 3 o! the drawing wherein a portion of the circuit of Figure 1 is shown. Figure 3 shows also the arrangement of the cathode ray tube serving tor recording and transmitting oi the images produced by stylus 6. The cathode ray tube is indicated by Its cathode is indicated by 2|. In front oi the cathode the control electrode 22 is arranged, and succeeding this electrode, an electron lens 28, a cylinder 24 and an anode 25 are located. The plate is succeeded by two pairs of deflecting plates 28. A direct potentialsource 28 is provided for producing the anode potential and the partial potentials required for the other electrodes, a voltage divider 21 being inserted in the circuit oi said direct potential source. The positive pole of battery 28 is grounded so that plate 25 is also at ground potential. Control electrode 22 is connected to the negative pole-of 28 through a resistance 28. Resistance 29 is bridged by 'a switch 88 which, on the one hand, is connectedvto that end of resistance 28 which is directly connected to the control electrode 22. As can be seen from Figure 3 the control electrode 22 is negatively biased in regard to cathode 2| so that the cathode ray is not able to produce an electron beam and a spot on the luminescent screen of tube The potential between the control electrode and the cathode may amount to approximately 12 v., for example. Whenrelay winding 9 exertsattracting power due to operation of stylus 6, it closes switch 30 and, consequently, a less negative potential in regard to the cathode is imparted to the control electrode, for instance, a potential of only 4 v. Thus a cathode ray beam is produced and the tube is ready for operation.

According to Figure 4, relay actuating means consists of elements 3| to 89, 3| being a resistance, 32 an electron tube with plate33, control grid 34 and cathode 35, 36 indicating a battery biasing control grid 34 negatively in regard to cathode to such an extent that the tube cannot pass any current. 38 indicates the plate battery and 8 represents a current-sensitive electromagnetic relay of lower sensitivity which, for instance, exerts attracting power at a current of 30 ma. and more, and closes switch 38 according to Figure 3. The whole arrangement represents a device for amplifying the-current passing through 8| proasa'aosa ducing a corresponding control potential at resistance 81 which makes the grid more positive to such an extent thata strong current is passed by the tube. In this case, a much stronger current flows through the plate circuit or tube 82 than through resistance 3| so that a less sensitive relay 8 is operated by the plate current than may be operated directly. This arrangement is preterably used when it does not appear suitable to feed the current of approximately 1 ma. flowing through stylus i directly to an electromagnetic relay 0! corresponding sensitivity as in Figure 3. g

The subject matter of the application is par-- ticularly well suited for the direct transmission at distance of script, drawings, signatures (in banks for instance), for reducing the scale 0! drawings or enlarging, and the like. when transmitting such configurations this extremely simple apparatus will be preferred as compared with the known complicated television arrangements which serve for transmitting moving images having many details.

As regards the manufacture of transmission apparatus according to the invention, it is advisableto make the entire apparatus exclusive ofthe tube so that it may be connected to any desired cathode ray tube.

I claim: 7 v

1. A cathode ray telautograph system comprising a cathode ray, means in said tube for developing a beam oi electrons, means for deflecting the beam in substantially mutually perpendicular directions, said last named means including beam deflecting means, a source or potential, a stylus and a resistance area whereby the potential applied to the deflecting means and accordingly the deflection of the cathode ray beam may be controlled in accordance with the position of the stylus on the resistance area, and means for preventing the development of the beam 0! electrons when the stylus is-removed from the resistance area comprising a relay responsive to the current present in the stylus circuit.

2. A telautograph comprising a cathode ray tube including means for producing a beam of electrons of small cross-sectional area, means responsive to the presence of the produced cathode ray beam, and means for deflecting the cathode ray beam in substantially mutually perpendicular directions, said means including beam deflecting plates, a source of potential, a stylus, and a resistance area whereby the potential applied to the deflecting plates and accordingly the deflection of the cathode ray beam and its position on the beam responsive means may be determined by the position 0! the stylus on the resistance area, means for normally biasing the cathode ray beam to beam cut-oi! and means including a relay for permitting the production of a cathode ray beam wherebythe beam may be produced only when the stylus is in contact with the resistance area.

ERICI-I HANDRICK. 

